The present invention relates to a paper-copy output apparatus such as an inkjet printer or facsimile machine. More particularly, the invention concerns a thermal-compression type of fluid jetting apparatus employed in a print head of such a print output apparatus. The invention also concerns a method of making paper copies by means of such an apparatus.
Generally, a fluid jetting apparatus employed in a print head of an output apparatus such as an inkjet printer or a facsimile machine, ejects ink in from ink chamber outward through a nozzle by exerting physical force to the ink chamber. Such fluid jetting apparatuses include thermal type, piezoelectric, and thermal-compression devices to exert the physical force to eject the fluid.
One thermal-compression fluid jetting apparatus of the prior art is shown in FIG. 1. The fluid jetting apparatus includes a driver module 20, a membrane 30, and a nozzle module 40.
Driver module 20 includes a substrate 15, a fluid chamber subassembly 25 having a plurality of working fluid chambers 27, a plurality of heating elements 16 disposed within the respective working fluid chambers, and a plurality of electrodes 17 connected with the respective heating elements.
Nozzle module 40 includes an ink chamber subassembly 45 having a plurality of ink chambers 57, and a nozzle plate 47 connected to an upper side of the ink chamber. Nozzle holes 49 are formed on the upper side of the nozzle plate, corresponding in location to the respective ink chambers.
Membrane 30 is disposed between the ink chamber and the fluid chamber. The membrane serves the function of partition between the working fluid chambers and the ink chambers.
Substrate 15, fluid chamber subassembly 25, membrane 30, and ink chamber subassembly 45 have correspondingly located ink feeding holes 11, 21, 31, and 41, which intercommunicate with one another. Ink feeding hole 41 of the ink chamber communicates with the ink chambers via an ink feeding passage 59. Ink feeding hole 11 of substrate 15 communicates with an external ink source (not shown). Accordingly, the ink is fed from the external ink source into the ink chambers through the feeding holes 11, 21, 31, and 41, and ink feeding passage 59.
Nozzle plate 47, ink chamber 45, membrane 30, and fluid chamber member 25 have corresponding fluid feeding holes 53,43, 33, and 23, which communicates with one another. Fluid feeding hole 23 of the fluid chamber intercommunicates with the working fluid chambers through a fluid feeding passage 29. The working fluid is charged in the working fluid chambers through fluid feeding holes 53, 43, 33, and 23, and fluid feeding passage 29. Fluid feeding hole 53 of the nozzle plate is sealed to be air-tight by a sealing member 55, after working fluid is charged in the working fluid chambers 27, fluid feeding passage 29 and fluid feeding holes 23, 33, and 43.
When electricity is applied to electrodes 16, heating elements 17 generate heat. The working fluid in the working fluid chambers is heated, forming bubbles. The bubbles increase the volume of the working fluid chambers, upwardly pressing and curving membrane 30. Accordingly, the ink in the ink chambers is pushed and jetted through nozzle holes 49.
The foregoing conventional fluid jetting apparatus, however, has a shortcoming of complicated manufacturing processes. It requires a process for separately preparing the ink and the working fluid, and a sealing process after the working fluid is discharged into the working fluid chambers. Further, since the working fluid employs an organic solvent such as a heptane which is apt to evaporate easily, there is a likelihood of having unnecessary space in the working fluid chambers. When the space is formed in the working fluid chambers, the intensity of the pressure exerted on membrane 30 during the heating of heating elements 16 becomes insufficient, so that the quantity of the jetted ink can not be precisely controlled.
In order to solve the problem of the conventional fluid jetting apparatus, the same applicant has previously disclosed a xe2x80x98Thermal-compression type fluid jetting apparatusxe2x80x99, which utilizes ink as the working fluid as shown in FIG. 2.
As shown in FIG. 2, a substrate 115, a fluid chamber subassembly 125, a membrane 130, and an ink chamber subassembly 145 have corresponding ink feeding holes 111, 121, 131, and 141 which intercommunicate. Ink feeding hole 141 of the ink chamber subassembly communicates with ink chambers 157 through an ink feeding passage 159. Ink feeding hole 121 of fluid chamber subassembly 125 communicates with working fluid chambers 127 through an ink feeding passage 129. Accordingly, ink chambers 157 and working fluid chambers 127 communicate with one other.
Ink feeding hole 111 of substrate 115 communicates with an external ink source. The ink is fed from the ink source to working fluid chambers 127 and ink chambers 157 through ink feeding holes 111, 121, 131, and 141, and ink feeding passages 129 and 159. The ink fed into the working fluid chambers 127 is the working fluid.
As electricity is applied to electrodes 116, heating elements 117 generate heat. As described earlier, the ink in the ink chambers is pushed, and is then jetted out through the nozzle holes by the deformation of the membrane. In such an ink jetting apparatus, since the ink is used as the working fluid, there is no need to separately prepare the working fluid, and also no need for the sealing process. Also, the malfunction of the ink jetting apparatus is prevented.
The above-described ink jetting apparatus utilizing the ink as the working fluid, however, has the following problem: While the ink in working fluid chambers 127 is pushed out by the expansion of the bubble produced due to the heating of the heating elements, there is no constant supply of ink thereto. Accordingly, the pressure of the ink jetting decreases, and the quantity of the jetted ink becomes insufficient. As a result, the print quality deteriorates, especially in continuous performance of the printing operation.
Further, the repetitive heating of the heating elements 117 increases the temperature in the working fluid chambers, and the durability of the fluid jetting apparatus is shortened due to the excessive heat.
Accordingly, an object of the present invention is to provide a fluid jetting apparatus having a consistently high print quality by maintaining a constant ink jetting pressure, and also having longer durability by preventing excessive heat.
The above object is accomplished by a thermal compression type fluid jetting apparatus including a nozzle part, a driving part, and a membrane. The nozzle part includes an ink chamber for reserving the ink, and a nozzle hole for permitting the ink in the ink chamber to be jetted therethrough. The driving part has a heating element received in the working fluid chamber, forming a working fluid chamber. The membrane serves as a partition between the ink chamber and the working fluid chamber. During the heating operation of the heating element, the membrane is curved by the increased pressure in the working fluid chamber, and thus pressurizes ink in the ink chamber. The working fluid chamber includes an ink feeding hole formed thereon for receiving ink from an external ink source, and the ink chamber includes an intercommunicating passage which communicates with the working fluid chamber. Accordingly, the ink fed into the working fluid chamber is fed into the ink chamber through the intercommunicating passage.
In the ink jet process of the present invention, the ink is constantly fed into the working fluid chamber. As a result, the possible pressure decrease and excessive heat in the working fluid chamber are prevented.